Dry torque motor servo valve

ABSTRACT

A servo valve is disclosed having a dry electrical torque motor operating an armature which controls a flapper valve, an o-ring for sealing the dry torque motor from the flapper valve, a boost valve responsive to the output from the flapper valve, and a feedback spring responsive to the movement of the boost valve for repositioning the armature controlling the flapper valve. Moreover, the electrical torque motor includes a pair of low reluctant bars joining the like poles to increase the electromotive force exerted upon the armature.

United States Patent 11 1 Amdur July 31, 1973 [54] DRY TORQUE MOTOR SERVO VALVE 3,390,613 7/1968 Westbury et al 137/83 X .4 r v 3,542,051 11/1970 McFadden et 31.. [751 Inventor? Amdur Luls Pall 2,725,040 11/1955 Harris 137/83 x Mlnn. [73 Assignee: Honeywell Inc., Minneapolis, Minn. P i E i fl T, Kli k i k [22] Filed Dec 20 1971 Attorney-Lamont B. Koontz et al.

21 A 1. No.: 210 060 1 pp 57 ABSTRACT [52] U.S. Cl. 137/625.62 A Servo valve is disclosed having a dry electrical ""1 51 1111. c1. FlSb 9 00, Fl6k 11/07 Operating armature which commls a PP 58 Field of Search 137/83, 85,82,625, valve Hing sealing the dry torque from 37/62. 251 /303 the flapper valve, a boost valve responsive to the output from the flapper valve, and a feedback spring respon- 56] References Cited sive to the movement of the boost valve for reposition- UNITED STATES PATENTS ing the armature controlling the flapper valve. Moreover, the electrical torque motor includes a pair of low 2,337,;24 15/1967 Zeunfr .1 137/6256? X reluctant bars joining the like poles to incl-ease the 1 3,5 3 gz i z mf 54 electromotive force exerted upon the armature. 3,141,383 7/1964 Abild 137/85 X 3,216,440 11/1965 Kohman 137/82 7 Chums 4 Draw as 45 43 l Patented July 31, 1973 3,749,129

2 Sheets-Sheet 1 Patented July 31, 1973 3,749,129

2 Sheets-Sheet 2 DRY TORQUE MOTOR SERVO VALVE This invention relates to improvements in electrically operated fluid handling servo valves.

When using a torque motor to control a hydraulic valve, it is desirable to provide a dry chamber for the torque motor. Some of the advantages in using a dry torque motor include easy accessability to the torque motor and less resistance to armature movement. Because a dry torque motor is used, some means must thereby be provided to seal the dry torque motor from the fluid handling valve.

The prior art, as shown in US. Pat. Nos. 2,924,241 and 3,095,906, have relied on either a flexture tube or a diaphragm to seal the dry torque motor from the hydraulic servo valve. However, these two types of sealing means are undesirable since they are expensive and do not lend themselves to the torque motor of the instant invention.

These prior art disadvantages have been overcome by placing an O-ring in the device to seal the torque motor from the valve. The O- ring is placed in the plane which is normal to the armature at its pivot point and, in such a position, the O-ring results in negligible hysteresis. Since the O-ring does not suffer any flexture, no hysteresis results and the O-ring does not interfere with the operation of the torque motor.

Another improvement made over the prior art relates to the torque motor itself. One prior art torque motor places a U-shaped north pole magnetic structure on one side of the armature and a U-shaped south pole magnetic structure on the other side of the armature. The armature in this arrangement pivots about a point which is between the two poles. If the pivot is outside of the pole structure, this arrangement results in the magnetic forces exerted on the armature opposing each other and requires more current to move the armature a given distance.

The prior art, as shown in the US. Pat. No. 3,095,906 overcame this disadvantage by positioning an armature between two magnets such that the top portion of the armature lies in a gap which is formed by the north pole of one magnet and the south pole of the other. The lower portion of the armature is positioned in a gap formed by the south pole of the first magnet and the north pole of the second magnet. Thus, the forces exerted on the armature by the magnetic structure will be additive rather than subtractive and result in greater efficiency. Also, this arrangement allows for the pivot point to be closer to the middle of the armature thus balancing that armature.

In this prior art arrangement, however, it is noted that the flux must travel through the permanent magnets. Permanent magnets are a high reluctance material and, therefore, impede the flow of flux through the magnetic structure. Applicant has found that by connecting the north poles together and by connecting the south poles together with bars of a low reluctance material, the flux flow will be increased resulting in an increase in the electromotive force exerted on the armature.

Other objects and advantages will be apparent from the following detailed description and accompanying drawing in which:

FIG. 1 is a vertical sectional view through the electrohydraulic servo valve of this invention.

FIG. 2 is a hydraulic circuit schematic of the present invention.

FIG. 3 is a view showing the magnetic structure of the electrical torque motor.

FIG. 4 is a view showing an alternative placement of the sealing ring.

In FIG. 1, reference numeral 10 denotes the electrical torque motor which is positioned above the flapper valve 11 which in turn operates the boost valve 12.

In particular, the electrical torque motor comprises a pair of permanent magnets 13 and 14. Permanent magnet 13 is magnetically associated with a pair of pole pieces 15 and 16 whereas permanent magnet 14 is magnetically associated with pole pieces 17 and 18. The permanent magnets are arranged such that pole pieces 15 and 18 are north poles and pole pieces 16 and 17 are south poles. Armature 19 is positioned in the gap formed between the pole pieces 15-18 and has a generally cup shaped projection 20 for cooperating with O- ring 22 and housing 23. The O-ring can take the shape of any other shape, i.e., a square ring, which is capable of providing a seal.

FIG. 4 shows an alternative method of sealing the torque motor from the hydraulic portions 11 and 12. In FIG. 4, an indent is formed in the armature l9 and a sealing ring 22' is placed in the indent and cooperates with housing 23 to form a seal.

The O-ring 22 seals the dry torque motor 10 from the hydraulic portion of the servo valve comprising flapper valve 11 and boost valve 12. The armature 19 extends down through the body 24 of the flapper valve 11. Positioned within the body portion 24 are channels 25 and 26 which terminate in nozzles 27 and 28 positioned opposite from each other and separated by the armature l9. Fluid is supplied to nozzles 27 and 28 from channel 29 through channel 30 such that whenever the armature is moved off of center, a differential pressure is established in nozzles 27 and 28 which pressures are transmitted to channels 25 and 26. A fluid amplifier is constructed into the bottom of body portion 24 and will be more fully described with respect to FIG. 2.

The channels 25 and 26 are connected to the control ports of this fluid amplifier whichhas its output ports connected to channels 31 and 32. Channels 31 and 32 cooperate with chambers 33 and 34, respectively, of the boost valve 12. Whenever a differential pressure exists in the chambers 33 and 34, spool 35 will move in such a direction as to reestablish equal pressures in chambers 33 and 34. Spool 35 has lobes or lands 36 and 37 spaced sufficiently apart to receive the end 38 of a feedback spring 39.

Supply port 40 supplies the hydraulic fluid to the boost valve 12 and will flow out of outlet ports 41 and 42 depending upon the position of the spool 35. The position of the spool 35 determines the extent that lands 43 and 44 cover outlet ports 41 and 42 respectively. Return ports 45 and 46 are positioned between lands 35 and 43, and 44 and 37 respectively to return the hydraulic fluid back to its reservoir.

The fluid from outlet ports 4] and 42 is fed to a cylinder 47 for positioning the output piston 48.

The operation of the circuit can be better understood from a review of FIG. 2 which has the same reference numerals as FIG. 1 when applicable. Fluid is supplied to the flapper valve 11 from supply port 40, through channel 29 and through channel 30. When an electrical signal is applied to the coil 49, armature 19 moves by a corresponding amount to establish a differential pressure in nozzles 27 and 28. This differential pressure is transmitted by channels 25 and 26 to input ports 50 and 51 of fluid amplifier 52. The power jet for the fluid amplifier is supplied from supply port 40 through fluid channel 53. The differential pressure established at ports 50 and 51 will cause deflection of the power jet and result in a differential fluid flow through outlet ports 54 and 55. The differential fluid flow output from the fluid amplifier results in a differential pressure in chambers 33 and 34 which causes movement of the spool 35. Movement of spool 35 results in the movement of lands 43 and 44 to establish a differential flow from the output ports 41 and 42.

Isolation chamber 56 of fluid amplifier 52 is connected by way of fluid channel 57 to the return ports 45 and 46.

As armature 19 is moved by the forces acting on it as a result of the energization of coil 49, projecting cup 20 ride over the O-ring 22 without causing flexture of the O-ring. The pivot point of the armature is located in the plane of the O-ring. Thus, the O-ring seals the dry torque from the hydraulic portion of the valve and is not subject to hysteresis, and the armature will always return to its neutral position upon deenergization of the coil 49 without any offset in its position.

When the spool valve 35 moves in response to a differential pressure in chambers 33 and 34, the feedback spring 39 will move by a corresponding amount to reposition the armature 19 to a position where the forces acting on the armature are balanced. Should the electrical signal to the coil 49 be changed, the forces will become unbalanced and the armature will again move.

Turning now to FIG. 3, there is disclosed the particular arrangement of the torque motor without the showing of the coil 49. The permanent magnet and pole piece arrangement is arranged such that pole pieces 15 and 18 are north poles and pole pieces 16 and 17 are south poles. As has been noted hereinbefore, the flux which will result from energization of coil 49 travels through the permanent magnet.

This flux flow can be greatly enhanced by providing an alternative low reluctance path to the flux rather than through the high reluctance path of the permanent magnets. Therefore, bar 58 of a low reluctance material is arranged such that it joins the south poles of permanent magnets 13 and 14 and bar 59 of a similar low reluctance material is arranged to join the north poles of permanent magnets 13 and 14.

Bars 58 and 59 allow the flux established by the coil 49 to pass through the circuit without going through the high reluctance paths of permanent magnets 13 and I4. Bars 58 and S9 allow a much smaller input signal to the coil 49 to move armature 19.

The embodiments of the invention in which an exclusive property or right is claimed are defined as follows:

1. An electro-hydraulic servo valve having an electrical portion and a hydraulic portion, said portions to be sealed from each other, said servo valve comprising:

electrical torque motor means including magnetic circuit means, coil means and movable means having an armature portion and a flapper portion, said magnetic circuit means and coil means cooperating with said armature portion for controlling movement of said movable means, said movable means having a pivot point between its armature portion and its flapper portion, said electrical torque motor means forming said electrical portion,

hydraulic means for receiving said flapper portion and including nozzle means positioned adjacent to said flapper portion, means for creating a flow of hydraulic fluid through said nozzle means dependent upon the position of said flapper portion with respect to said nozzle means, and means responsive to said fluid flow adapted to drive an output device, said hydraulic means forming said hydraulic portion, and

a ring of material for sealing said electrical portion from said hydraulic portion, said ring lying in the plane substantially normal to said armature means at said pivot point and cooperating with said movable means to provide a substantially nonhysteretic seal.

2. The electro-hydraulic servo valve of claim 1 wherein said ring of material comprises a flexible O- ring.

3. The electro-hydraulic servo valve of claim 2 wherein said armature is formed with a cup shaped projection and said O-ring is placed between said projection and said hydraulic portion.

4. The electro-hydraulic servo valve of claim 2 wherein said armature is formed with an indent and said O-ring is placed into said indent.

5. The electro-hydraulic servo valve of claim 1 wherein said responsive means comprises a boost valve having a spool movable in response to said fluid flow through said nozzle means and means for connecting said nozzle means to said boost valve.

6. The electro-hydraulic servo valve of claim 5 further comprising feedback means responsive to the movement of said spool for repositioning said flapper means in response to movement of said spool.

7. The electro-hydraulic servo valve of claim 6 wherein said ring of flexible material comprises a flexible O-ring.

# i i i t 

1. An electro-hydraulic servo valve having an electrical portion and a hydraulic portion, said portions to be sealed from each other, said servo valve comprising: electrical torque motor means including magnetic circuit means, coil means and movable means having an armature portion and a flapper portion, said magnetic circuit means and coil means cooperating with said armature portion for controlling movement of said movable means, said movable means having a pivot point between its armature portion and its flapper portion, said electrical torque motor means forming said electrical portion, hydraulic means for receiving said flapper portion and including nozzle means positioned adjacent to said flapper portion, means for creating a flow of hydraulic fluid through said nozzle means dependent upon the position of said flapper portion with respect to said nozzle means, and means responsive to said fluid flow adapted to drive an output device, said hydraulic means forming said hydraulic portion, and a ring of material for sealing said electrical portion from said hydraulic portion, said ring lying in the plane substantially normal to said Armature means at said pivot point and cooperating with said movable means to provide a substantially non-hysteretic seal.
 2. The electro-hydraulic servo valve of claim 1 wherein said ring of material comprises a flexible O-ring.
 3. The electro-hydraulic servo valve of claim 2 wherein said armature is formed with a cup shaped projection and said O-ring is placed between said projection and said hydraulic portion.
 4. The electro-hydraulic servo valve of claim 2 wherein said armature is formed with an indent and said O-ring is placed into said indent.
 5. The electro-hydraulic servo valve of claim 1 wherein said responsive means comprises a boost valve having a spool movable in response to said fluid flow through said nozzle means and means for connecting said nozzle means to said boost valve.
 6. The electro-hydraulic servo valve of claim 5 further comprising feedback means responsive to the movement of said spool for repositioning said flapper means in response to movement of said spool.
 7. The electro-hydraulic servo valve of claim 6 wherein said ring of flexible material comprises a flexible O-ring. 